Instantaneous selective protective arrangement for direct current networks



Dec. 13, 1932. A, B, R R 1,890,775

INSTANTANEOUS SELECTIVE PROTECTIVE ARRANGEMENT FOR DIRECT CURRENT NETWORKS Filed Sept. 10. 1951 y 9 coil may it e- 1932 UNITED STATES OFFICE,

nim- BAn'rEEnEMY FOURNIER, on .PARIS, FRANCE,- Assrcnon T'O' UNION DELEC- ITEIoI'rE, or rams, FRANCE, A conronarion or FRANCE msTAN'rANEoUs SELECTIVE PROTECTIVE ARRANGEMENT FOR manor CURRENT rnrwomrs Application filed September 10,1931, Serial ne. 5e2,184-,' and in- France September 26, 1930.

a The present invention has as object an instantaneous selective protective arrangement for direct current networks, against short circuits which may arise either'directly between the conductors or between these conductors and earth. a

The invention consists in utilizing the short period which succeeds the establishment of a short circuit and in causing arelease relay to function by means of anelectromotive i a force proportional to the sum of the variations (as a function of time) of the currents whichenter or leave each one of the extremities of thesection of the protected circuit. When. this relay is excited, it produces the simultaneous opening of all the circuit breakers placed at the various extremities of the protected section. 1 a y The rinciple of the invention will be better understood from the following descrip- 1 tion in relation to the annexed drawing;

In the drawing, 1 represents a continuous current conductor from which are derived a certain number of branches 2, 3 and 4. At each end for the conductor 1, serving for its rotection againstshortcircuits and at the beginning ofeach of the branches 2, 3 and l 4, circuit breakers 5,6, 7, 8 and 9 are placed.

These circuit breakers, furnished withtrip be of any type usually employed in practice. At each of the extremities of the conductor 1,and in each branch, .there are also installed current transformers 10, 11, 12, 13, 14 the primary circuits of which are ,each connected in series with the corresponding continuous current conductor. 1 The secondary windings of these current transform v ers are all connected, inparallel and feed the winding 15 ofa single relay 16. When the winding 15 is excited, the movable contact 17 of the relay 16 comes in contact with the fixed contact 18 of this relay which causes, by way of the connections19, the

6 identical characteristics.

simultaneous excitation ofrelease bobbins of interrupters 5, 6, 7, 8 and 9 and as aresult the opening of the latter.

The current transformers 10, 11, 12, 13 and 14 may be of any type but they must have According to a preferredmode of carrying out the invention,

the cores of thesefcurrent transformers in} clude a gap or are constitutedof non-mag: netic material which permits of avoiding the disturbances which would be caused by the more or less great saturation of the various cores and, as a result, of assuring a similar working ofall: the transformers. r he mode of working of the arrangement is then asfollowsz In the absence of any short circuit, the currents which flow in the primaries otthe current transformers being continuous currents, the .electromotive force. induced in the secondary of these transformers, proportion: al to the variation of the flux induced by the primary as a function of time, is nothing and the relay is not excited.

. section, for example in the sense of the arrows, is nothing and as a result the sum of the derivatives with respect to'time of these currents is also nothing. It results that the sum of electromotive force induced at the ter minals of the secondary of the current transformers is nothing and that the relay 16 is not excited. V e

V If, on the other hand, a short circuit is produced inthe conductor'l within the protected zone, the sum of the currents entering and leaving this zone is not nothing, nor is the sum of the derivatives with respect to time of these currents. The transitory period dur ing which the short circuit is established thus induces at the terminals of the secondaries of the current transformers electromotive forces of which the sum is not nothing and which cause the excitation of the relay 16 and as a result the simultaneous opening of the circuit breakers guarding the section.

' What I claim is 1.' Protecting system for a zone of direct current electric conductors comprising cir cuit breakers on each conductor inside said zone, for each circuit breakera 'trip coil, an electric power supply. able" to feedsaidcoils,

a relay controlling said feeding current, and 7 means for energizing said relay by a current proportional to the variations of the algebraic sum of the currents entering'the zone to be protected. .i 2. Protecting system for a zone of direct current electric conductors, comprising circuit breakers on-each conductor insidesaid zone, for each circuit breaker a trip coil, an electric power supply able to'feed said coils,

a relay controlling said fe'eding current, curc rent transformers all having thesa-mechan acteristics, the primary winding of each of which is inserted in one conductor at the point .wherethe same crosses the zone border and means to connect in parallel with the relay coil "thesecondary windings of said transformers.

3. Protecting system for a zone of direct I current electric conductors, comprising c1rcuit breakers on each conductor inside said zone, for each c1rcu1t breaker a trip c011, an

' electric power supply able to feed said coils,

a relaycontrolling said feeding current, currenttransformers Whose cores are constituted of non-magnetic material, all transformers having the same characteristics, the primary-Winding of each transformer being inserted in one conductor at the'point Where the said conductor crosses the zone border,

, and means to connect'in parallel with the relay coil the secondary windings of said transformers. I I

In testimony whereof 'I have aflixed my signature. I

Ami: BARTH'ELEMY'EOURNIER. I 

